1. Field of the Invention
This invention relates generally to electrical connectors for connecting electrical devices or parts to a cable harness, and more particularly to a connector assembly incorporating active and passive circuit elements for effectively isolating the electrical assembly with which the connector is used from electromagnetic interference (EMI), radio frequency interference (RFI), and electromagnetic transient pulses (EMP).
2. Discussion of the Prior Art
Present-day commercial and military aircraft incorporate complexed electronic control systems incorporating numerous sensors and force transducers as well as the electronics necessary for processing the sensor signals and developing the requisite control signals for the transducers so that the aircraft can be flown in a controlled manner. Typically, the electronic assemblies involved will be housed in metallic shielding enclosures or boxes which are adapted to slide into equipment racks on the aircraft. Each of the electronic modules will typically incorporate a receptacle having a large number of terminal pins arranged in a grid and which are appropriately wired to the electronic componentry within the shielded enclosure. Incorporated into the rack assembly is a plug member which is adapted to mate with the receptacle on the box housing the electronics module. The pins of the plug are typically connected to conductors in a wiring harness leading off to other electronic equipment which may be spread throughout the aircraft.
A standard plug used throughout the aircraft industry is referred to as the ARINC 600 plug, which meets the ARINC specifications for air transport avionics equipment interfaces. That specification, among other things, defines the number of pins, their location, the pin spacing and the shell dimensions for the plug. Those desiring specific information relative to the plug are referred to the ARINC 600 specification itself.
The ARINC 600 plug is designed to mate with a receptacle attached to or formed into a wall of the shielding enclosure in which the electronics are contained. The ARINC 600 plug includes three sections with sections A and B incorporating 150 male pins, each disposed in a grid array of rows and columns. Section C includes a smaller number of pins which, generally speaking, provide the power connections to the electronics module. The existing receptacle, designed to accept the plug, includes a plurality of terminal pins having female sockets on one end and male wire wrap terminals or solder points on the other end. The pins are arranged in the same grid array, such that when the plug is inserted into the receptacle, the male pins of the plug engage the female sockets of the receptacle's terminal pins. The male portion of the receptacle's terminal pins then connect to the wiring for the electronics within the shielded enclosure.
The above-described prior art plug/connector receptacle combination has a number of inherent drawbacks. First of all, the replacement of a connector receptacle because of a worn or damaged terminal pin involves the need to open the shielding enclosure and the disassembly of all of the wire wrap or solder connections from the connector receptacle. This is time consuming and may be quite costly in terms of the down-time for the involved aircraft.
Another drawback of the prior art ARINC 600 connector design is that it does not provide the necessary immunity of the electronic circuitry from the effects of EMI, RFI and EMP. Thus, for example, a lightning strike near the aircraft may induce a high voltage transient pulse (EMP) into the conductors of the wiring harness in the aircraft. Such transient pulses are oftentimes of an amplitude that can destroy CMOS circuitry forming a part of the electronics module with which the ARINC 600 connector is used. Similarly, EMI and RFI radiation in proximity to the module may find its way into the interior of the shielded enclosure via the connector assembly. These RFI/EMI and EMP sources may result in the electronic controls issuing erroneous data to the other electronic equipment with which it is associated, resulting in loss of control over the aircraft.
While filtering and transient suppression circuits have been devised for dealing with RFI/EMI and EMP radiation, physical space constraints may preclude inclusion of such circuitry within the electronics module. A need, therefore, exists for a connector plug receptacle assembly which can accommodate transient and noise suppression circuitry which can be replaced without having to enter the shielding enclosure containing the printed circuit cards and componentry. Moreover, the connector must be constructed such that it cannot allow erroneous data to be transmitted out to the devices being controlled.
There is disclosed in the Paul et al. U.S. Pat. No. 4,789,360 and the Morse et al. U.S. Pat. No. 4,746,310, each assigned to Amphenol Corporation, electrical connectors having transient suppression components incorporated therein. Moreover, the connector is designed such that the contact pins have mating forward and rearward end portions and a medial portion which includes a circuit protection element in the form of a silicon diode or varistor. Because of the manner in which the connector pins are designed, it is possible to remove the forward end portion to allow repair or replacement of the circuit detection component. The physical size of the silicon diodes and varistors and their mode of attachment to the connector pins drastically limits the number of pins that can be accommodated in a given area. Thus, the approach disclosed in those two Amphenol Corporation's patents is impractical in implementing a EMI/RFI/EMP connector receptacle compatible with the existing ARINC 600 plug having up to 300 plus pins in an area of only about 7 square inches.
Other prior art patents of interest are owned by International Telephone & Telegraph Corp. and include the Couper et al. U.S. Pat. No. 4,582,385, U.S. Pat. Nos. 4,600,262 and 4,572,600 to Nieman and the Brancaleone et al. U.S. Pat. No. 3,790,858. These patents describe a circumferential connector plug/receptacle combination in which an electrical component is mounted on the side of each contact. As with the Amphenol connectors described above, the approach used in the IT&T patents for achieving EMI/RFI/EMP protection is somewhat wasteful of real estate, making the approach practical only for connectors having relatively few contact pins embodied therein.